Embodiments of the disclosed technology relate to a transparent conductive thin film and method of manufacturing the same.
The pixel electrodes of a thin film transistor-liquid crystal display (TFT-LCD) device currently mainly employs indium tin oxide (ITO, In2O3:Sn) thin film produced by magnetron sputtering. Since this thin film contains rare element—indium (In), the manufacturing cost is increased. In addition, since target materials and manufacturing equipments used to produce such a thin film are generally expensive, the device cost is also increased.
As an alternative to the ITO thin film, tin dioxide (SnO2) thin film is used, which is a n-type semiconductor material with a band gap of 3.6 eV, has the advantages of high electron mobility (109.56 cm2/Vs), high carrier concentration (1.23×1019 cm−3), high transmittance, chemical stability at high temperature, and low raw material price, and is widely used for transparent conductive layers, gas sensitive devices, solar cells and electrodes of Lithium-ion battery.
Currently, the production of SnO2 thin films mainly adopts magnetron sputtering, low pressure chemical vapor deposition (LPCVD), high temperature spraying, sol-gel and so on. Among the above, LPCVD is most commonly used, and the raw material of such process is tin chloride (SnCl4) and hydrofluoric acid (HF), and there exists a problem that the costs of raw material and equipment are relatively high.
Compared with other several methods, the sol-gel method has the advantages of simplicity, low cost, high efficiency, easy doping, and abliligy to be coated on irregular shape devices and to produce uniform thin films of large area. The raw materials of this process are SnCl2.2H2O and SnCl4.5H2O. During the production of SnO2 thin film, a large amount of chlorine ion (Cl−) can cause non-stoichiometric ratio of doping, thereby it will influence the conductivity of the formed thin film. Meantime, the solution obtained after the raw materials are mixed must be kept at a particular acidity (pH=1˜2) so as to prevent the strong hydrolysis reaction of SnCl2.2H2O and SnCl4.5H2O. However, in producing pixel electrode of a TFT-LCD device by using such a method, the acid environment can corrode gate electrodes and data lines formed in the TFT-LCD device, which therefore limits the application of such a method in the production of pixel electrodes of the TFT-LCD device.